1. Field of the Invention
The present invention relates to a micro-electromechanical device, a liquid discharge head, and a method of manufacture therefor.
2. Related Background Art
The liquid discharge head, which is one example of the micro-electromechanical device used conventionally. for an ink jet printer or the like, is such that liquid in each of the flow paths is heated and bubbled by means of heating elements, respectively, and that liquid is discharged from each of the discharge ports by the application of pressure exerted when liquid is bubbled. Each of the heating elements is arranged on an elemental substrate, and driving voltage is supplied to each of them through wiring on the elemental substrate.
For a liquid discharge head of the kind, there is a structure in which a movable member is arranged in the flow path in a cantilever fashion where one end of the movable member is supported. One end (fixedly supported portion) of this movable member is fixed onto the elemental substrate, while the other end (movable portion) is made extendable into the interior of each liquid flow path. In this manner, each movable member is supported on the elemental substrate with a certain gap with the surface thereof, and arranged to be displaceable in each flow path by the pressure exerted by bubbling or the like.
For the conventional example described above, the wiring is formed, on the elemental substrate. The wiring is extremely thin, and its resistance value is great. Then, from this elemental substrate, the wiring is connected with the external driving circuit or the like. However, with such large resistance value of the wiring, the electrical loss becomes great inevitably. Also, in order to make the resistance value smaller even by a slight amount, the wiring should preferably be made flat and wide. As a result, the liquid discharge head is formed in a larger size inevitably.
Now, therefore, the present invention is designed with a view to solving the problems discussed above. It is an object of the invention to provide a micro-electromechanical device capable of reducing the electrical loss of wiring without making the structure complicated or making the size of the device large. It is also the object of the invention to provide a liquid discharge head and a method of manufacture therefor.
In order to achieve the object of the invention discussed above, it has a feature given below.
The micro-electromechanical device of the present invention comprises a fixedly supporting portion and a movable portion, and a substrate for supporting the movable member which is supported in a state having a specific gap with the substrate. For this device, a metallic layer which provides the gap for the movable portion is covered by the fixedly supporting portion of the movable member, and remains to be used as a wiring layer.
Also, the wiring layer is electrically connected with a plurality of wiring provided for the substrate.
Another feature of the- present invention is the provision of a liquid discharge head comprising an elemental substrate; a ceiling plate laminated on the elemental substrate; a flow path formed between the elemental substrate and the ceiling plate and a movable member each having a fixedly supporting portion and a movable portion, the movable portion of which is positioned in each of the flow paths. Here, the movable member is supported in a state having a specific gap with the elemental substrate. For this liquid discharge head, a metallic layer for providing the gap for the movable portion is covered by the fixedly supporting portion of the movable member, and remains to be used as a wiring layer.
Also, this liquid discharge head, a heating element is provided for the elemental substrate corresponding to the flow path, and the aforesaid wiring layer may be electrically connected with the heating element through wiring.
With the structure thus arranged, at least a part of the metallic layer that forms a sufficiently thick gap can be utilized as wiring, hence making it possible to reduce the value of electric resistance.
Also, a method of the present invention for manufacturing a liquid discharge head, which is provided with an elemental substrate, a ceiling plate laminated on the elemental substrate, and a flow path formed between the elemental substrate and the ceiling plate, comprises the steps of forming a metallic layer for the formation of a gap on the elemental substrate; forming a thin film layer on the metallic layer to become a movable member removing a portion of the metallic layer positioned below the movable portion of the movable member, while keeping the portion of the movable member positioned below the fixedly supporting portion to remain intact; and making at least a part of the remaining portion of the metallic layer as a wiring layer to be electrically connected with the wiring pattern on the elemental substrate.
Here, the thin film layer is formed by SiN, and the metallic layer is formed by Al or may be formed by Al alloy.
In this respect, the term xe2x80x9cupstreamxe2x80x9d and the term xe2x80x9cdownstreamxe2x80x9d referred to in the description hereof are used to express the flow direction of liquid from the liquid supply source toward the discharge ports through the bubbling areas (or movable members) or to express the structural directions.